【作者】 郭铁能；

【导师】 李俊峰； 陆秋海；

【作者基本信息】 清华大学 ， 力学， 2007， 博士

【摘要】 空间柔性结构的振动控制是航天结构研究的重要领域。本文理论和实验研究了大型空间柔性结构主动拉索改造的可行性和结构振动抑制的有效性,并分析了主动拉索振动控制中自身稳定性问题。本文首先对带拉索的航天大柔性结构进行了分类,并探讨了主动拉索改造的可行性。为了解决如何选择已有拉索进行主动拉索改造问题,本文引入了量化指标-可控Grammian因子来衡量拉索改造后的可控性。在一个中心刚体带两对称柔性附件的常见航天器模型主动拉索改造方案择优问题上,通过计算四种改造方案的可控Grammian因子,找出了最为理想的改造方案。在主动拉索改造之中,为了不影响结构原来的构形,本文提出一种无预紧力的主动拉索控制方式。同时考虑到其力驱动元件输出力有限,则主动拉索控制器是一个单边饱和非线性作动器。本文采用一种分段非二次型性能指标,推导了带单边饱和约束最优控制方法,并证明了带有状态观测器的最优控制的稳定性。气浮台上卫星模型实验验证了文章所提的主动拉索方法及最优控制律的设计。本文针对难以准确数学建模的复杂空间柔性结构,利用主动拉索上的拉力变化进行反馈,通过控制主动拉索端部位移来增加结构阻尼从而抑制结构振动。本文提出了两种控制算法:比例积分控制算法和力反馈微分控制算法。这两种方法均不需要受控结构的数学模型,同时控制算法不存在控制溢出,且均能显著增加结构的阻尼。JPL-MPI缩尺模型上的数值仿真结果表明两种控制算法均能显著抑制结构振动。主动拉索具有良好的控制性能。但在振动控制中主动拉索上是一个时变的力,当拉索横向受到干扰之后容易产生自激振动。本文建立了主动拉索横向振动的动力学模型,通过约束参数法解析给出了拉索物理参数与稳定区域的关系,并采用绝对节点坐标有限元法对解析得到的稳定区域进行验证。有限元仿真结果与理论分析结果能较好地吻合。因此,解析结果能有效指导主动拉索设计,可以避免控制中拉索自身不稳定问题。更多还原

【Abstract】 The vibration control of the flexible space structure (FSS) is an important field in aerospace research. This paper focuses in exploiting the potential of the cables in the structures, in which the cable acts as active tendons, and researches on the feasibility of the active tendons to suppress the vibration of the FSS by both analytical and experimental approaches, and analyzes the stability of the active tendon in vibration suppression.First, the FSS with cables is introduced systematically. The feasibility of substituting active tendon for some existing cables on the FSS is discussed. The controllability grammian factor is adopted to quantitatively evaluate the controllability of the active tendons. The generic spacecraft model with a central rigid body and two flexible appendages is used to study the proposed method. Four installation methods of active cables are introduced and the controllability grammian factors are used to determine the optimal one.Non-preloaded tendons are adopted to attenuate the vibration of the FSS. Non-preloaded tendons do not deteriorate the configuration of the FSS, but the non-preloaded tendon, which can only provide pulling force, is a unilateral non-linearity actuator. In addition, the force saturation property caused by limited power of the controller adds the complexity to the controller design. As a result, a piecewise cost function is introduced to derive the optimal control law, and the stability of the control law with the acceleration feedback is discussed. The verification experiment on a pneumatic suspension table demonstrates the effectiveness of the proposed non-preloaded tendon and the control law for vibration suppression of flexible spacecraft, though the actuator can only work in half a vibration cycle due to its unilateral character.In order to control the vibrations of complex FSS with active tendon, the force on the preloaded tendon of the FSS is adopted to act as feedback signals and the tip movement of the active tendon is used to active displacement. A proportional-integral force feedback algorithm and a differential force feedback control algorithm are presented to increase the damping of the FSS. The two control algorithms, which require no structure model, can provide high damping ratio for the space structure. The stability of the control system is then shown. The simulation results on the structure similar to JPL-MPI demonstrate the effectiveness of the proposed algorithms for vibration control of the space structure.The active tendon has excellent performance for the vibration suppression of the FSS. But the time-varying force on the cables may cause self-excitation vibration, which will deteriorate the effectiveness of the control system. Therefore, the stability of the active tendon should be evaluated before controller design. The governing equation of the cable is derived to discuss the analytical relationship between the stable region and the physical parameters of the tendon by the method of strained parameters. The absolute nodal co-ordinate formation finite element method (FEM) is adopted to verify the stable region derived from the above analytical method. The simulation results of the FEM show that the analytical result can be used to direct the design of the active tendon to avoid the instability.更多还原